The fundamentals works to read to understand 20th Century Philosophy

Wide-ranging texts:

• Philosophical Explanations (Robert Nozick, 1981)
• Invariances: The Structure of the Objective World (Robert Nozick, 2001)
• Mortal Questions (Thomas Nagel, 1979)
• Must We Mean What We Say?: A Book of Essays (Stanley Cavell, 1976)

Political Philosophy:

• A Theory of Justice (John Rawls, 1971) + Justice as Fairness: A Restatement (John Rawls, 2001)
• Anarchy, State, and Utopia (Robert Nozick, 1974)
• The Open Society and Its Enemies, Vol. 1 & 2 (Karl Popper, 1945)

Idealism and its critics:

• Geschichte und Klassenbewußtsein (György Lukács, 1923)
• La filosofia dell’assurdo (Giuseppe Rensi, 1937)
• La persuasione e la rettorica (Carlo Michelstaedter, 1910)

Phenomenology:

• Logische Untersuchungen, Vol. 1 & 2 (Edmund Husserl, 1900/01)

The so-called Positivism:

• Logisch-Philosophische Abhandlung (Ludwig Wittgenstein, 1921)
• Der Logische Aufbau der Welt (Rudolf Carnap, 1928)

Nominalism:

• The Structure of Appearance (Nelson Goodman, 1951)

Modal Realism:

• On the Plurality of Worlds (David K. Lewis, 1986)

Aesthetics (and Art Epistemology):

• Music and the Ineffable (Vladimir Jankélévitch, 1961)
• Languages of Art (Nelson Goodman, 1976)
• Illuminationen (Walter Benjamin, 1955)

The so-called Analytical Philosophy:

• Philosophische Untersuchungen (Ludwig Wittgenstein, 1953)
• Modalities: Philosophical Essays (Ruth Barcan Marcus, 1993)
• Naming and Necessity (Saul A. Kripke, 1980)

Neopragmatism:

• Word and Object (Willard Van Orman Quine, 1960)
• Philosophy and the Mirror of Nature (Richard Rorty, 1979)

Logic:

• Kurt Gödel Collected Works Vol. 1 (Publications 1929-1936)
• Kurt Gödel Collected Works Vol. 2 (Publications 1938-1974)
• Logic, Semantics, Metamathematics: Papers from 1923 to 1938 (Alfred Tarski, 1956)

Philosophy of Science:

• Logik der Forschung (Karl Popper, 1934)
• Conjectures and Refutations (Karl Popper, 1963)
• Truth and Beauty (Subrahmanijan Chandrasekhar, 1973)

Moral Philosophy:

• Reasons and Persons (Derek Parfit, 1984)
• Ethics: Inventing Right and Wrong (J. L. Mackie, 1977)

Russell:

• The Basic Writings of Bertrand Russell, 1903-1959
• Human Knowledge: Its Scope and Value (Bertrand Russell, 1948)
• A History of Western Philosophy (Bertrand Russell, 1945)

Consciousness & Cognition:

• Autopoiesis and Cognition (Humberto R. Maturana & Francisco J. Varela, 1973)
• Content and Consciousness (Daniel Dennett, 1986)
• The Mind Doesn’t Work That Way (Jerry A. Fodor, 2000)